Question

why maximum number of electrons accommodated in outermost orbit is 8 whereas m shell can have 18

Answer 1

BCOZ THE NUMBER OF ELECTRONS IN A SHELL IS DETERMINED BY THE FORMULAE 2n SQUARE, WHERE n IS THE NUMBER OF THE PARTICULAR SHELL i. e: 1st shell or 2nd shell etc;

Answer 2

Answer:

However if you consider the first 18 elements of the periodic table, the maximum number of electrons found in the m-shell is 8.

This is because of the fact that electrons are filled in shells in the increasing order of energy.

So, first the shells are filled in the order k, then l, and finally m.

The K and L shells together can hold 10 electrons. And hence electrons begin to occupy the m-shell only in the elements with atomic number 11 - 18.

And since the element with atomic number 18 has only 8 electrons left, these 8 electrons occupy the m-shell.